The use of a deoxygenating agent would render anaerobic the inside of closely packaged food such as noodles, rice, fish, flesh and fowl and paste products thereof, fermented food, rice cakes, Japanese-and Western-style confections and smoked food, to thereby significantly inhibit the growth of aerobic microorganisms such as molds. Since it apparently seems that the shelf life of each food product is significantly prolonged thereby, deoxygenating agents have been widely applied to a number of closely packaged foods.
Conventional deoxygenating agents are mainly composed of, for example: (a) in iron powder and a metal halide; (b) a ferrous compound and an alkaline material such as sodium acetate decahydrate, sodium sulfate decahydrate or an alkali hydroxide; (c) an organic reducing material such as ascorbic acid and an alkaline material; or (d) hydrosulfite and an alkaline material. However it has been found that there are many microorganisms capable of vigorously growing under an anaerobic condition so that no practically sufficient shelf life can be achieved only by using a deoxygenating agent in many cases. Thus we have occasionally proposed to employ ethyl alcohol, which can enhance antibacterial activities under an anaerobic condition, together with a deoxygenating agent. This process is now being widely accepted.